Your runtime seems to be looking for ioser12.dll (Win32) or (lib)ioser12.so (*nix), a native library usually found in your JRE's bin directory (Win32) or in the JRE lib (*nix). This can be caused by finding another j2ee.jar or jndi.jar outside of the JBoss distribution but in your classpath. At least that is normally where this problem arises.

ioser12 handles RMI-IIOP so it's fairly important for J2EE stuff.

The other thing is that you may not actually have the ioser12 native libraries.